This inventor and his former coworkers have a number of patents related to air enrichment of biodegradable waste using aerobic bacteria in waste water. Among those patents are the following: Blough, U.S. Pat. No. 5,194,144, issued Mar. 16, 1993; Blough, U.S. Pat. No. 5,951,867, issued Sep. 14, 1999; Blough, U.S. Pat. No. 6,245,237, issued Jun. 12, 2001; Hoage, U.S. Pat. No. 6,461,500, issued Oct. 8, 2002; and Hoage, U.S. Pat. No. 6,884,353, issued Apr. 26, 2005. The most recent issued of this group is U.S. Pat. No. 6,461,500 and its divisional method case U.S. Pat. No. 6,884,353, both containing an identical disclosure. These two patents relate to the use of the combination of an air plate and a particular shape of impeller to achieve air bubbles of greater than 100 micron size dispersed throughout waste water, kept in place by Brownin movement to enhance lateral oxygen transfer to replace oxygen consumed by aerobic bacteria in the biodegradation process. While this device works, there is an increasing need for continuing improvement, ideally with devices of decreased horsepower and increased ability to result in stable entrained air in order to replenish oxygen consumed by the rapidly growing and multiplying aerobic bacteria as they degrade waste material.
The creation of the ideal device to accomplish substantial decreases in BOD involves an understanding of mechanics/physics of bubbles, as they exist for example in waste lagoons or lakes, ponds, etc. This understanding then allows development of the most efficient mechanical device.
Once air is entrapped in waste water, there is a rapid development stage resulting in a cloud of bubbles. Some bubbles will be several millimeters in diameter, but others will be smaller. Each bubble is buoyant and will tend to rise towards the surface. As bubbles become smaller, small particles and dissolved organic compounds very often collect on the surface of the bubble while it is submerged. Gas will be exchanged slowly across the surface of the bubbles resulting in a continual evolution of the size and composition of each bubble. In general, in these devices air is really entrapped by an enclosure of a large air volume in a contained zone but is usually drawn into the interior (entrained) where there is intense and convergent flow of water. The device of the present invention results in very small or microbubbles, that is, less than 100 microns in size. In affect, what can be called “minibubble clouds” are created around the device resulting in enhanced air gas exchange. As aerobic bacteria multiply using the 8-10 parts per million of oxygen that are dissolved in water at standard temperature and pressure, oxygen in the entrained air dissolves in the water to replenish that portion consumed by the aerobic bacteria which multiple exponentially creating an ever increasing demand for more oxygen. The device of the present invention improves upon U.S. Pat. No. 6,461,500 and serves the need for meeting the increased oxygen demand necessary for the aerobic bacteria to do their work to decrease the parts per million of BOD in waste water.
Accordingly, it is a primary objective of the present invention to improve upon the device of my prior art existing inventions to provide an aeration unit which consumes less horsepower, and which has the highest degree of lateral oxygen transferred in order to replace oxygen used by aerobic bacteria during the digestion process. The process enhances the production of small microbubbles less than 100 microns in size throughout the waste water.
The method and means for accomplishing the above primary objective and advantage as well as others will become apparent from the detailed description of the invention which follows hereinafter.